Ensuring Process Stability with Reactor Temperature Control S
plays an important role in industrial
processes, pilot plants, and chemical and pharmaceutical
laboratories. When controlling reactors, both exothermic and
endothermic reactions must be offset with high speed and
reliability. Therefore, different conditions and effects must be
taken into account when specifying an optimum and highly dynamic
temperature control system.
Temperature Control of Reactors
temperature control systems
are used with
chemical reactors made of either steel or glass. Th
e former is more rugged and long-lasting, while the latter enables
chemists to observe processes inside the reactor.
However, in the case of glass reactors, extensive precautions have
to be followed for safe usage. Reactors usually include an inner
vessel to hold the samples, which need temperature control. This
inner vessel is enclosed by a jacket containing heat-transfer
liquid. This reactor jacket is linked to the
In order to control the reactor’s temperature, the temperature
control system pumps the heat-transfer liquid through the reactor’s
jacket. Rapid temperature change inside the reactor is balanced by
instant cool-down or heat-up, and the liquid is either cooled or
heated inside the temperature control system. Figure 1 shows a
schematic of a simple temperature control system.
Figure 1. Functional view of reactor temperature
Both materials and reactor design can affect the
of highly dynamic reactor systems. However, the heat
transferred by a glass-walled vessel will be different than that
transferred by a steel-walled vessel. In addition, both wall
thickness and surface area can also affect accuracy. Therefore,
proper mixing of the initial materials inside the reactor is
important to obtain good uniformity, which in turn will guarantee
optimal heat exchange.
For each type of reactor, maximum pressure values have been
provided as per the specifications established by reactor
manufacturers and in the Pressure Equipment Directive 97/23/EG.
Regardless of any temperature control application, these limit
values may not be surpassed during operation under any situations.
Prior to starting a
temperature control application, the
applicable limits must be programmed within the temperature control
Another important criterion in reactors is the maximum permissible
temperature difference, which is referred to as Delta-T limit. It
defines the highest difference between the temperature of the
contents of the reactor and the actual thermal fluid
When compared to steel reactors, glass reactors are more
susceptible to thermal stress. For that matter, any temperature
control system should enable users to program reactor-specific
values for the Delta-T limit per time unit. Within the
temperature control equipment
components considerably affect the stability of the process and
these include heat exchanger, pump, and control electronics.
It is important to ensure that a temperature control system has
sufficient heating and cooling capacity, as this can significantly
affect the speed to reach the preferred temperatures. In order to
determine the preferred heating and cooling capacities, users must
consider the essential differences in temperature, the volume of
the samples, the preferred heat-up and cool-down times, and the
specific heat capacity of the temperature control medium.
Highly dynamic temperature control solutions
commercially available in the market with water or air cooling.
Air-cooled systems do not utilize water and may be deployed where
there is sufficient air flow.
The heat thus removed from the reactor is eventually transferred to
ambient air. Water-cooled systems need to be joined to a cooling
water supply, but they operate more quietly and do not add surplus
heat in small labs. These units could be completely enclosed by the
application, if required.
The integrated pump of the
temperature control unit
must be sufficiently strong to obtain the
preferred flow rates at stable pressure. To ensure that pressure
limit values mentioned above are not exceeded, the pump should
provide the preferred pressure quickly and with maximum
Operating conditions and pressure specifications of the reactor
must always be taken into account, and regulation of pump capacity
must be done by presetting a limit value. Sophisticated
temperature control solutions
include pumps that
balance the variations of the viscosity of the heat transfer liquid
to make sure that energy efficiency is maintained
This is because viscosity influences flow and hence the heat
transfer. An additional advantage provided by magnetically coupled
pumps is that they guarantee a hydraulically-sealed thermal
circuit. Also, self-lubricated pumps are beneficial as they require
only minimum maintenance.
The closed loop circuit prevents contact between the ambient air
and the heat transfer liquid. This not only prevents permeation of
oxidation and moisture, bit also prevents oil vapors from entering
into the work environment.
Additionally, an internal expansion vessel must permanently absorb
temperature-induced volume variations inside the heat exchanger.
Individual cooling of the expansion vessel will help in ensuring
temperature control unit
does not overheat
and ultimately ensures operator safety.
A temperature control equipment should operate consistently even at
high ambient temperatures. In majority of cases, the real work
environment will diverge from the ideal temperature of 20°C. During
hot summer months, temperature control solutions are exposed to
adverse conditions. In laboratories, ambient temperatures are
usually higher because of energy saving measures. These instances
demonstrate the benefits of temperature control solutions that work
consistently at temperatures as high as 35°C.
Temperature control equipment
includes advanced control
electronics that monitor and control the process inside the reactor
and also the internal processes of the system. When a control
variable changes, the system is capable of readjusting the variable
to the setpoint sans overshooting.
Accurate control electronics are needed to maintain the stability
of a temperature control application. One option to assess control
electronics is to look at the effort needed to set parameters. In a
temperature control unit, users can enter a setpoint. Control
electronics must be self-optimizing throughout the temperature
control process to ensure optimum results.
To sum up, the process safety and stability during reactor
temperature control relies on the effectiveness of heat transfer,
the type of reactor, and the efficiency of the components within
the temperature control unit. Therefore, different conditions and
effects must be considered when specifying a highly dynamic
temperature control system.